A consortium of private equity firms including the Carlyle Group, Texas Pacific Group and the principal investment area of Goldman Sachs, have teamed up to bid for four of the five National Grid Transco gas networks in what would be Europe's largest buy-out transaction.

Last April Ofgem, the energy regulator, valued each of the five networks at between £691m (€1bn) and £1.8bn and revealed that the cheapest four were valued at £3.8bn.